Power supply controller having analog to digital converter

ABSTRACT

A power supply control method of performing a feedback control of an output voltage based on a deviation signal for a standard voltage value serving as a target value for the output voltage and a digital signal generated by analog/digital (A/D) conversion of the output voltage, the method includes selecting a range of the reference voltage for the A/D conversion based on the digital signal in a power supply startup period, and selecting a range of the reference voltage for the A/D conversion based on the deviation signal or a signal corresponding to the deviation signal in a steady state period.

The present application is a Divisional Application of U.S. patentapplication Ser. No. 12/461,655, filed on Aug. 19, 2009, which is basedon Japanese patent application No 2008-221496, filed on Aug. 29, 2008,the entire contents of which is incorporated herein by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a digitally-controlled power supplycontroller and power supply control method, and relates in particular tocontrol technology for an A/D (analog/digital) converter for digitallycontrolled power supplies.

2. Description of Related Art

In recent years, digitally controlled power supply controllers are beingutilized to extend the operating time of mobile devices such as cellulartelephones that have become widely used. In digitally controlled powersupply controllers, an A/D converter carries out sampling to sample theoutput voltage. Sampling with a high-resolution A/D converter must beperformed in order to suppress fluctuations in the output voltage. Indigitally controlled power supply controllers have problems withhigh-speed startups and regulating the startup speed of the supplyvoltage when switching between applications using different voltages.

FIG. 7 is a block diagram of the A/D converter of a related artdescribed in Japanese Patent Application Laid Open No. 2006-140819.

An A/D converter 1 contains a sample hold circuit 3, a D/A converter 4,a comparator 5, and a successive comparator control circuit 10. Thesuccessive comparator control circuit 10 includes a maximum settingvalue register 11, a minimum value setting register 12, a successivecomparator register 15, and a CPU (not shown in drawing) for performingA/D conversion processing. The maximum value register 11 and a minimumvalue setting register 12 are connected to a data bus 6 and an addressbus 7.

FIG. 8 and FIG. 9 illustrates the A/D conversion processing implementedby the CPU in the successive comparator control circuit 10. The CPU setsthe maximum value (Vmax register value) stored in maximum value settingregister 11 as a temporary maximum value Vmax for the reference voltage(S201). The CPU sets a minimum value (Vmin register value) stored in theminimum value setting register 12, as a temporary minimum value Vmin forthe reference voltage (S202). The CPU next processes these temporarilyset maximum value Vmax and minimum value Vmin, adjusting them for use asreference voltage that can be output by the DAC4 (S203-S208). The CPUfirst of all decides whether or not the minimum value Vmin temporarilyset in S202 and subtracted from the temporary maximum value Vmax set inS201, can be expressed as a power-of-two. The CPU in other words,decides whether the minimum value Vmin is divisible by two (S203 in FIG.9). If the CPU decides the value is divisible by two (S203: Y), then theprocessing proceeds to S209 (FIG. 8). If the CPU decides the value isnot divisible by two (S203: N) then a minimum increase/decrease widthVlsb determined by the conversion accuracy is added to the maximum valueVmax, and this summed value is then set as the maximum value Vmax(S204).

When the maximum value for a settable reference voltage is 5 V at aconversion accuracy of four bits, then the minimum increase/decreasewidth Vlsb at which the reference voltage can be increased or decreasedis 0.625 V (=5 V/8). The CPU next decides whether the maximum valuesVmax required via S204 have all become a “1” or not. The CPU in otherwords decides whether the upper limit of the settable maximum Vmax valuehas been reached (S205). If decided that the upper limit has not beenreached (S205: N), then the processing returns to step S203, and adecision made on whether the value found from subtracting the minimumvalue Vmin from the maximum value Vmax found in S204 is divisible by twoor not. If that value cannot be divided by two (S203: N), then theminimum increase/decrease width Vlsb is again added to the maximum valueVmax (S204). The maximum value Vmax is in other words repeatedlyincreased within a range that does not exceed the upper limit, and whenthe value found from subtracting the minimum value Vmin from the maximumvalue Vmax reaches a figure divisible by two (S203: Y), then theprocessing proceeds to S209.

If the CPU decides that the upper limit of the maximum value Vmax wasreached (S205: Y), then a value found from subtracting the minimumincrease/decrease width Vlsb from the minimum value Vmin temporarily setearlier in S202 (FIG. 8) is set as a new minimum value Vmin (S206). TheCPU next decides whether the minimum values Vmin found in S206 are allzeroes or not in other words decides whether the lower limit for thesettable minimum value Vmin was reached or not (S207). If decided thatthe lower limit was not reached (S207: N), then the CPU decides whetherthe maximum value Vmax, or in other words whether the value found fromsubtracting the minimum value Vmin found in S206 from the upper limit isdivisible by two or not (S208). Here, if decided that value is notdivisible by two (S208: N), then the minimum increase/decrease widthVlsb is once again subtracted from the minimum value Vmin (S206). Inother words, if in a range not reaching the lower limit then the minimumvalue Vmin is repeatedly decreased, and when the value found fromsubtracting the minimum value Vmin from the maximum value Vmax reaches avalue divisible by two (S208: Y), then the processing proceeds to S209.

In other words, the range of reference voltages outputted from DAC4 isset automatically based on the maximum value (Vmax register value) andminimum value (Vmin register value) input by the user.

The CPU next calculates the value obtained from summing the maximumvalue Vmax and the minimum value Vmin found in S203-S208 by two, or inother words, calculates the center value Vmid of the maximum value Vmaxand the minimum value Vmin (S209). Next, (5 V+0 V)/2=2.5 V is calculatedfor the case where the maximum value Vmax for example is 5 V, and theminimum value Vmin is 0 V. The successive comparator control circuit 10at this time outputs a digital output code for outputting referencevoltages corresponding to the center value Vmid to the DAC4 as a controlsignal. The DAC4 in this way performs digital/analog (DA) conversion ofthe DAC control signal that was input, and outputs to the comparator 5these reference voltages corresponding to center value Vmid.

The comparator 5 then compares the reference voltage (Vmid) outputtedfrom the DAC4, with the analog input voltage Vin held by the S/H circuit3, and outputs a signal corresponding to those comparison results to thesuccessive comparator circuit 10. The CPU then decides whether thesignal outputted from the comparator 5 shows comparison results suchthat the analog input voltage. Vin is larger than the reference voltage(Vmid) or not (S210). lithe comparison results show the analog inputvoltage Vin is larger than the reference voltage (Vmid) (S210: Y), thenthe reference voltage (Vmid) is set to a new minimum value Vmin (S211).If for example, the analog input voltage Vin is 3 V, and the referencevoltage (Vmid) is 2.5 V, then the CPU decides that the analog inputvoltage Vin is larger than the reference voltage (Vmid) (S210:Y), andthe 2.5 V of the reference voltage (Vmid) is set to a new minimum valueVmin (S211).

If the CPU decides that the comparison results show that the analoginput voltage Vin is smaller than the reference voltage (Vmid) (S210:N),then the reference voltage (Vmid) is set to a new maximum value Vmax(S212). If for example, the analog input voltage Vin is 2 V, and thereference voltage (Vmid) is 2.5 V, then the CPU decides that the analoginput voltage Vin is smaller than the reference voltage (Vmid) (S210:N),and the 2.5 V of the reference voltage (Vmid) is set to a new minimumvalue Vmin (S212).

The CPU next decides if the value found from subtracting the minimumvalue Vmin from the maximum value Vmax has become the minimumincrease/decrease width Vlsb or not. In other words, the CPU decideswhether the center value Vmid for the maximum value Vmax and minimumvalue Vmin is in a state that cannot be calculated (S213). For example,if the conversion accuracy (resolution) is 4 bits, maximum value Vmax is5 V, the minimum value Vmin is 0 V, then the 0.625 V (=5 V/8) becomesthe minimum increase/decrease width Vlsb so that the CPU decides if thevalue found from subtracting minimum value Vmin from the maximum valueVmax is 0.625 V or not (S213).

If the CPU here decides that the center value Vmid cannot be calculatedin this state (S213:N), then the process returns to S209 and centervalue Vmid is again calculated and a comparison made with that centervalue Vmid (S210). If for example, the analog input voltage Vin is 3 V,and the minimum value Vmin newly set previously in S211 is 2.5 V, thenthe CPU calculates that the center value Vmid=(5 V+2.5 V)/2=3.75 V(S209), and compares the analog input voltage of 3 V with the centervalue of 3.75 V (S210). The CPU therefore compares the analog inputvoltage Vin with the reference voltage (Vmid) as described above (S210),and based on those comparison results decides a new minimum value Vminor maximum value Vmax (S211, S212) and calculates a new center valueVmid based on the minimum value Vmin or maximum value Vmax that weredecided (S209). The CPU repeats this processing that compares the analoginput voltage Vin with the reference voltage (Vmid) that is the newcenter value Vmid (S210).

Then, when the CPU decides the center value Vmid is in a state thatcannot be calculated (S213:Y), it stores, a conversion value VSAR neededfor finding the maximum value Vmax used in the final comparison in S213in SAR15 (S214).

The range of the reference voltage (Vmid) required for making thecomparison is set in this way based on the maximum value Vmax andminimum value Vmin set by the user, and set so as not to makecomparisons with reference voltages (Vmid) outside this range.

SUMMARY

The related Art has a problem that normal A/D conversion of outputvoltages in digitally-controlled power supplies was impossible if theoutput voltages are outside the reference voltage range during A/Dconversion.

A power supply controller includes an analog to digital (A/D) converterthat performs analog-digital conversion of an output voltage and outputsa digital signal, a deviation signal generator unit that generates adeviation signal from the digital signal and a standard voltage valueserving as an output voltage target value, and a power controller unitthat controls the output voltage based on the deviation signal. Thepower supply controller includes a conversion range setting unit thatsets a range of the reference voltage into the A/D converter based on afirst signal as the digital signal in a power supply startup period, andsets the reference voltage range into the A/D converter based on asecond signal as the deviation signal or as a signal corresponding tothe deviation signal in a steady state period.

The power supply control method of the present invention is a feedbackcontrol method that regulates the output voltage based on a deviationsignal for a standard voltage value serving as the target output voltagevalue, and a digital signal generated by A/D conversion of the outputvoltage; and in which the reference voltage range for A/D conversion isselected during the power supply start up period based on the digitalsignal and, the reference voltage range for A/D conversion is selectedin the steady state period based on a signal using the deviation signalor on the deviation signal. This type of method allows quick powersupply voltage startups.

The present invention provides a power supply controller and a powersupply control method that achieves quick power supply startups.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other exemplary aspects, advantages and features of thepresent invention will be more apparent from the following descriptionof certain exemplary embodiments taken in conjunction with theaccompanying drawings, in which:

FIG. 1 is a block diagram of the power supply controller of a firstexemplary embodiment of the present invention;

FIG. 2 is a chart showing the interrelation of conversion range with theapplicable input signal in the A/D converter of the power supplycontroller of the present invention;

FIG. 3 is a timing chart for the conversion range setting operationperformed by way of the PWM duty data in the A/D converter of the powersupply controller of the present invention;

FIG. 4 is a flow chart showing the operation for controlling the offsetin the A/D converter of the power supply controller of the presentinvention.

FIG. 5 is a block diagram of the power supply controller of a secondexemplary embodiment of the present invention;

FIG. 6 is a timing chart of the conversion range setting operation byway of the PWM duty data in the A/D converter of the power supplycontroller of the second exemplary embodiment of the present invention;

FIG. 7 is a block diagram of the A/D converter for a related art;

FIG. 8 is a flow chart for the successive comparison operation of theA/D converter of the related art; and

FIG. 9 is a flow chart showing the flow of setting of the range of thereference voltage outputted from the DAC in the A/D converter of therelated art.

DETAILED DESCRIPTION OF THE EXEMPLARY EMBODIMENTS First ExemplaryEmbodiment

FIG. 1 is a block diagram of the power supply controller of a firstexemplary embodiment. A power supply controller 100 includes: an inputpower supply 101, an inductor 103, a capacitor 106, and A/D converter107, a clock generator circuit 125, a deviation signal generator unit150, a power supply controller unit 160 and conversion range settingunit 170. The deviation signal generator unit 150 includes a computingcircuit 109 and a standard voltage 110, and generates a deviation signalfrom the standard voltage 110 and the A/D converter output 108 outputtedfrom the A/D converter 107. The power controller unit 160 contains aswitching transistor 102, a switching transistor driver 105, a powercontroller circuit 112, and a PWM generator circuit 114, and regulatesthe output voltage 104 based on the deviation signal generated by thedeviation signal generator unit 150. The conversion range setting unit170 contains a holding circuit 116, a computing unit 117, a selector118, a computing unit 120 as well as the range information 121.

The output signal from the switching transistor driver 105 serving as aswitching circuit and input voltage 101 is inputted to the switchingtransistor 102. The output signal from the switching transistor 102 isinputted to the inductor 103. The output signal from the inductor 103 isinputted to the capacitor 106 and the A/D converter 107. The inductor103 and the capacitor 106 here smooth the output signal from theswitching transistor 102, and the voltage after smoothing is set as theoutput voltage 104.

The A/D converter 107 inputs or receives the maximum voltage value 122and minimum voltage value 123 that were input from the output voltage104 and computing unit 120, and outputs a digital signal for the A/Dconverter output 108, to the computing circuit 109 and the holdingcircuit 116. The holding circuit 116 retains the inputted A/D converteroutput 108, and outputs a holding circuit output 127 to the selector118. The computing circuit 109 receives the standard voltage 110 servingas the target value for the output voltage 104 and the A/D converteroutput 108, and outputs the difference voltage 111 serving as thedeviation signal, to the power controller circuit 112. The powercontroller circuit 112 inputs the difference voltage 111 and the rangeinformation output 124 serving as the output signal from the rangeinformation 121 and outputs a data signal 113 serving as the signalaccording to the deviation signal, to the PWM generator circuit 114 andto the computing unit 117.

The range information output 124 is also simultaneously inputted to theselector 118. The data signal 113 is inputted to the PWM generatorcircuit 114 which outputs the PWM signal 115 to the switching transistordriver 105. The PWM signal inputted to the switching output transistor105 is output to the switching transistor 102. The data signal 113outputted from the power controller circuit 112 is also sent to anotherinput which is the computing unit 117. The data signal 113 and thecomputing unit clock 126 outputted from the clock generator circuit 125are inputted to the computing unit 117 and the computing unit 117outputs a computing unit output 128 to the selector 118.

An output signal from the holding circuit 116 and an output signal fromthe computing unit 117 are inputted to the selector 118, and theselector 118 outputs a selector output 119 to the computing unit 120.The selector output 119 that is outputted from the selector 118 and thecomputing unit clock 126 that is outputted from the clock generatorcircuit 125 are inputted to the computing unit 120, and the computingunit 120 outputs a maximum voltage value 122 and a minimum voltage value123 to the A/D converter 107, and also outputs a signal to the rangeinformation 121.

FIG. 2 is a chart showing the interrelation of conversion range and theapplicable input signal in the A/D converter of the power supplycontroller of the first exemplary embodiment. In this description, theminimum value of the input range of the A/D converter 107 is referred toas Vmin, and the maximum value as Vmax. The power supply controller 100switches among the four ranges of a first range R1, a second range R2, athird range R3, and a fourth range R4, in the startup period TW401. Inthe first range R1, an eleventh voltage value V11 is set in Vmax; and afirst voltage value V1 is set in Vmin. In the second range R2, aneleventh voltage value V11 is set in Vmax; and a third voltage value V3is set in Vmin. In the third range R3, an eleventh voltage value V11 isset in Vmax; and a fifth voltage value V5 is set in Vmin. In the fourthrange R4, an eleventh voltage value V11 is set in Vmax; and a seventhvoltage value V7 is set in Vmin.

In the steady state period TW402, the power supply controller 100switches among the three ranges consisting of the fourth range R4, thefifth range R5, and the sixth range R6. In the fifth range R5, aneleventh voltage value V11 is set in Vmax; and a ninth voltage value V9is set in Vmin. In the sixth range R6, an eleventh voltage value V11 isset in Vmax; and a tenth voltage value V10 is set in Vmin.

The operation of the power supply controller of the first exemplaryembodiment is described next while referring to FIG. 1 and FIG. 2. Inthe startup period TW401 of output voltage 104, the conversion rangesetting unit 170 retains the A/D converter output 108 in the holdingcircuit 116, selects the holding circuit output 127 by way of theselector 118 and outputs it to the computing unit 120. Determining theVmin for the next A/D conversion processing from the selector output 119in computing unit 120 sets the reference voltage range for the next A/Dconversion processing.

In the steady state period TW402 of output voltage 104, the conversionrange setting unit 170 utilizes the data signal 113 in the computingunit 117 to calculate the increase/decrease width of output voltage 104in the next A/D conversion process. The selector 118 selects thecomputing unit output 128 as the calculation results and outputs them tothe computing unit 120. Determining the Vmin for the next A/D conversionprocessing from the selector output 119 in computing unit 120 sets thereference voltage range for the next A/D conversion processing.

The range information output 124 is utilized to switch the selector 118in the startup period TW401 and the steady state period TW402. In thestartup period TW401, the range information 121 shifts from the startupperiod TW401 to the steady state period TW402 by setting the conversionrange setting to the fourth range R4, and the range information output124 is switched by selector 118 so as to output the computing unitoutput 128 to the selector output 119.

The A/D converter 107 has a two bit quantization resolution function.The operation in which the A/D converter output 108 sets the offset inthe startup period TW401 is described using conversion processing in avoltage range of 0 to 4 V as an example. In this description, XXb (Xindicates 0 or 1) represents the binary notation.

In the initial A/D conversion process, conversion is performed in thefirst range R1 by two bit quantization resolution. In the first rangeR1, the first voltage value V1 is set in Vmin, and the eleventh voltagevalue V11 is set in Vmax. The first voltage value V1 is 0 V, the secondvoltage value V2 is 1 V, the third voltage value V3 is 2 V, the fifthvoltage value V5 is 3 V, and the eleventh voltage value V11 is 4 V. Therelation of the output voltage 108 to the A/D converter output 104 istherefore such that: the first voltage value V1−second voltage value V2will be 00b, the second voltage value V2−third voltage value V3 will be01b, the third voltage value V3−fifth voltage value V5 will be 10b, andthe fifth voltage value V5−eleventh voltage value V11 will be 11b, andthe resolution will be 1 V.

When the A/D converter output 108 was 10b or 11b during conversion inthe first range R1, then in the next A/D conversion processing, two bitconversion will be performed on the second range R2 set with Vmin atthird voltage value V3, and Vmax at the eleventh voltage value V11. Whentwo bit conversion was performed in the first range R1, and the A/Dconverter output 108 was 00b or 01b, then the next A/D conversionprocessing will be performed in first range R1 the same as in theprevious A/D conversion processing and set with Vmin at the firstvoltage value V1, and Vmax at the eleventh voltage value V11.

When conversion by two bit quantization resolution (hereafter, two bitquantizing) was performed in the first range R1, and the A/D converteroutput 108 was 10b or 11b, then in the next A/D conversion processing,two bit quantizing will be performed in the second range R2, and thethird voltage value V3 will be 2 V, the fourth voltage value V4 will be2.5 V, the fifth voltage value V5 will be 3 V, the seventh voltage valueV7 will be 3.5 V, and the eleventh voltage value V11 will be 4 V. Therelation of the output voltage 104 to the A/D converter output 108 willtherefore be such that: the third voltage value V3−fourth voltage valueV4 will be 00b, and the fourth voltage value V4−fifth voltage value V5will be 01b, the fifth voltage value V5−seventh voltage value V7 will be10b, and the seventh voltage value V7−eleventh voltage value V11 will be11b, and the resolution will be 0.5 V.

When conversion by two bit quantizing was performed in the second rangeR2, and the A/D converter output 108 was 10b or 11b, then in the nextA/D conversion processing, two bit quantizing will be performed in thethird range R3, set with Vmin at the fifth voltage value V5, and Vmax atthe eleventh voltage value V11. In the conversion performed in thesecond range R2, and the A/D converter output 108 was 00b or 01b, thenthe next A/D conversion processing will be performed in the second rangeR2 the same as in the previous A/D conversion processing and set withVmin at the third voltage value V3, and Vmax at the eleventh voltagevalue V11.

When conversion by two bit quantizing was performed in the second rangeR2, and the A/D converter output 108 was 10b or 11b, then the fifthvoltage value V5 will be 3 V, the sixth voltage value V6 will be 3.25 V,the seventh voltage value V7 will be 3.5 V, the ninth voltage value V9will be 3.75 V, and the eleventh voltage value V11 will be 4 V. Therelation of the output voltage 104 to the A/D converter output 108 willtherefore be such that: the fifth voltage value V5−sixth voltage valueV6 will be 00b, and the sixth voltage value V6−seventh voltage value V7will be 01b, the seventh voltage value V7−ninth voltage value V9 will be10b, and the ninth voltage value V9−eleventh voltage value V11 will be11b, and the resolution will be 0.25 V.

When conversion by two bit quantizing was performed in the third rangeR3, and the A/D converter output 108 was 10b or 11b, then in the nextA/D conversion processing, two bit quantizing will be performed in thefourth range R4, set with Vmin at the seventh voltage value V7, and Vmaxat the eleventh voltage value V11. When conversion by two bit quantizingwas performed in the third range R3, and the A/D converter output 108was 00b or 01b, then the next A/D conversion processing will beperformed in the third range R3 the same as in the previous A/Dconversion processing and set with Vmin at the fifth voltage value V5and Vmax at the eleventh voltage value V11.

When conversion by two bit quantizing was performed in the third rangeR3, and the A/D converter output 108 was 10b or 11b, the seventh voltagevalue V7 becomes 3.5 V, the eighth voltage value V8 becomes 3.625 V, theninth voltage value V9 becomes 3.75 V, the tenth voltage value V10becomes 3.875 V, and the eleventh voltage value V11 becomes 4 V. Therelation of the output voltage 104 to the A/D converter output 108 willtherefore be such that: the seventh voltage value V7−eighth voltagevalue V8 will be 00b, the eighth voltage value V8−ninth voltage value V9becomes 01b, the ninth voltage value V9−tenth voltage value V10 becomes10b, the tenth voltage value V10−eleventh voltage value V11 becomes 11b,and the resolution will be 0.125 V.

FIG. 3 is a timing chart for the conversion range setting operation bythe PWM duty data in the present invention. Operation of the steadystate TW402 that determines the conversion range of the A/D converter107 based on the data signal 113 is described. At the sampling timingT601, the A/D converter 107 sets the tenth voltage value V10 to Vminusing the computing unit 120, and the output voltage 104 is sampled inthe sixth range R6 with the eleventh voltage value V11 set to Vmax bythe computing unit 120. The power controller circuit 112 outputs a datasignal 113 for the output voltage sampled at the sampling timing T601 tothe computing unit 117 as data D601.

The power controller 112 inputs the data signal 113 into the computingunit 117 at timing T602. The computing unit 117 calculates the range ofoutput voltage 104 regulated by the PWM signal 115 based on this datasignal 113, and outputs a computing unit (clock) output 128. The outputvoltage 104 range is changed based on duty of the PWM signal 115. Theselector 118 utilizes the range information output 124 to output thesetting range data C601 calculated in selector output 119, to thecomputing unit 120.

At timing T603, the computing unit 120 calculates the maximum voltagevalue 122 serving as Vmax and the minimum voltage value 123 serving asVmin set in A/D converter 107 based on the setting range data C601. TheVmax is here clamped at 4 V serving as the eleventh voltage value V11 sothe processing only calculates the Vmin, and the seventh voltage valueV7 is output to the minimum voltage value 123.

At the next sampling timing T604, the A/D converter 107 samples theoutput voltage 104 in the fourth voltage range R4 where the seventhvoltage value V7 is set to Vmin by way of the computing unit 120, andthe eleventh voltage V11 is set to Vmax by way of the computing unit120. The power controller circuit 112 outputs the data signal 113 forthe output voltage 104 sampled at the sample timing T604, as the dataD602 to the computing unit 117.

At the timing T605, the data signal 113 is inputted to the computingunit 117. The computing unit 117 calculates the range of the outputvoltage 104 regulated by the PWM signal 115, based on the data signal113, and outputs it as a computing unit output 128. The range of theoutput voltage 104 is changed based on the duty of PWM signal 115. Theselector 118 outputs the setting range data C602 calculated in selectoroutput 119 to the computing unit 120.

At the timing T606, the computing unit 120 calculates the minimumvoltage value 123 serving as Vmin, and the maximum voltage value 122serving as Vmax for setting in the A/D converter 107, based on thesetting range data C602. The Vmax is here clamped at 4 V serving as theeleventh voltage value V11 so the processing only calculates the Vmin,and the ninth voltage value V9 is output to the minimum voltage value123.

In the next sampling timing T607, the A/D converter 107 samples theoutput voltage 104 in the fifth range R5 where the ninth voltage V9 isset to Vmin by way of the computing unit 120 and the eleventh voltagevalue V11 is set to Vmax by the computing unit 120. The power controllercircuit 112 outputs the data signal 113 for the output voltage 104sampled at the sampling timing T607, to the computing unit 117 as thedata D603.

At the timing T608, the data signal 113 is inputted to the computingunit 117. The computing unit 117 calculates the range of the outputvoltage 104 controlled by the PWM signal 115 based on the data signal113, and outputs it as the computing unit output 128. The range ofoutput voltage 104 is changed based on the duty of the PWM signal 115.The selector 118 outputs the setting range data C603 calculated inselector output 119 to the computing unit 120.

At the timing T609, the computing unit 120 calculates the minimumvoltage value 123 serving as Vmin and the maximum voltage value 122serving as Vmax for setting in the A/D converter 107 based on thesetting range data C603. The timing from T601 to T609 is repeated fromhere onwards.

FIG. 4 is a flow chart of the offset control operation of the presentinvention. The operation for setting the offset based on the A/Dconverter output 108 in the initial startup period TW401 is describednext.

The computing unit 120 first of all initializes the range informationsetting it to 0. The selector 118 input at this time, is switched to theoutput of holding circuit 116. The power controller circuit 112 startscontrol based on the 0 output of range information output 124, andresponds to operation in the startup period. (S101). The A/D converter107 performs A/D conversion processing (S102).

If the second bit of A/D converter output 108 is 1, then the processshifts to step S104, and if the second bit is 0 then the process shiftsto step S102 (S103).

If the range information 121 is 0, then the process shifts to step S105,and if the range information 121 is other than 0 then the process shiftsto step S107 (S104).

If the range information 121 is 0 then an addition is made to the firstoffset value, setting the third voltage value V3 in the minimum voltagevalue 123, and based on the range information output 124 being 0, thepower controller circuit 112 starts executing control in response tosetting the third voltage value V3 as the offset value (S105).

The range information 121 is incremented and the process shifts to stepS102 (S106).

If the range information 121 is 1, then the process shifts to step S108,and if the range information 121 is other than 0 or 1 then the processshifts to step S110 (S107).

If the range information 121 is 1, then an addition is made to thesecond offset value, setting the fifth voltage value V5 in the minimumvoltage value 123 and, based on the range information output 124 being1, the power controller circuit 112 starts executing control in responseto setting the fifth voltage value V5 as the offset value (S108)

The range information 121 is incremented and the process shifts to stepS102 (S109).

If the range information 121 is 2, then the process shifts to step S111,and if the range information 121 is other than 2, then the processshifts to step S101 (S110).

If the range information 121 is 2, then an addition is made to the thirdoffset value, setting the seventh voltage value V7 in the minimumvoltage value 123, and based on the range information output 124 being2, the power controller circuit 112 starts executing control in responseto setting the seventh voltage value V7 as the offset value (S111).

The range information 121 is incremented and the process shifts to stepS113 (S112).

The range information output 124 switched the selector 118 to thecomputing unit 117 output, and functions in response to operation insteady state period (S113).

The operation for setting the offset based on the data signal 113, inthe steady state period TW402 from step S114 onward is described next.

If the data signal 113 exhibits a duty of 0 to 25 percent, then theprocess shifts to step S115, and if other than a duty of 0 to 25 percentthen the process shifts to step S116 (S114). A value corresponding to aduty of 0 to 25 percent is set in the minimum voltage value 123 and theprocess shifts to step S114 (S115). If the data signal 113 exhibits aduty of 26 to 50 percent, then the process shifts to step S117, and ifdata signal 113 exhibits a duty other than 26 to 50 percent then theprocess shifts to step S118 (S116). A value corresponding to a duty of26 to 50 percent is set in the minimum voltage value 123 and the processshifts to step S114 (S117).

If the data signal 113 exhibits a duty of 51 to 75 percent, then theprocess shifts to step S119, and if other than a duty of 51 to 75percent then the process shifts to step S120 (S118). A 51 to 75 percentduty value is set in the minimum voltage value 123 and the processshifts to step S114 (S119). A value corresponding to a duty of 76 to 100percent is set in the minimum voltage value 123 and the process shiftsto step S121 (S120). If the output voltage 104 is 0, then the processingis terminated, and if other than 0 then the process shifts to step S114(S121).

The steps S101-S112 correspond to the operation in the startup periodTW401, and the steps S114-S121 correspond to the operation in the steadystate period TW402. Step S113 is a step for switching the operationbetween the startup period TW401 and the steady state period TW402.

The power supply controller of the first exemplary embodiment asdescribed above is therefore capable of a quick power supply voltagestartup by setting the range of the reference voltage based respectivelyon the A/D converter output signal in the power supply startup period;and the deviation signal or a signal using the deviation signal in thesteady state period. Moreover, normal A/D conversion process is achievedwithout deviating from the reference voltage range since the minimumvoltage value is changed without changing the maximum voltage value.

Controlling the minimum voltage value acts to narrow the referencevoltage range as the output voltage approaches the steady state period.Therefore even A/D converters with a quantizing function of a few bitscan attain high-resolution A/D conversion in the steady state period. Inother words a reference voltage range that maintains high resolution canbe set.

Moreover, even A/D converters with a 2 bit quantizer function can attaina quantizing resolution of five bits in the steady state period so thata high resolution effect can be achieved at low current consumption.

Second Exemplary Embodiment

FIG. 5 is a block diagram of the power supply controller of a secondexemplary embodiment. The power supply controller 200 shown in FIG. 5,is the power supply controller shown in FIG. 1 but further including anupper limit voltage setting table 201. Other sections of the structureare assigned the same reference numerals (as the first exemplaryembodiment) so their description is omitted. In this structure, themaximum voltage value 122 outputted from the computing unit 120, isinputted to the upper voltage setting table 201, and the upper limitvoltage value 202 and the minimum voltage value 123 are output to theA/D converter 107.

FIG. 6 is a timing chart of the operation for setting the conversionrange in the first exemplary embodiment by using the PWM duty data inthe A/D converter of the power supply controller of the presentinvention. The conversion range of A/D converter 107 is set based on thedata signal 113. The steady state period TW402 operation in FIG. 2 isdescribed.

At the sampling timing T801 in FIG. 6, the A/D converter 107 sets thetenth voltage value V10 in the Vmin by way of the computing unit 120,and samples the output voltage 104 in the sixth range R6 with theeleventh voltage value V11 set in the Vmax by the computing unit 120.The power controller circuit 112 outputs the data signal 113corresponding to the output voltage 104 sampled at the sampling timingT801 as the data D801 to the computing unit 117.

At the timing T802, the data signal 113 is input into the computing unit117. The computing unit 117 calculates the range of the output voltage104 controlled by the PWM signal 115 based on the data signal 113, andoutputs a computing unit (clock) output 128. The range of the outputvoltage 104 is changed based on duty of the PWM signal 115. The selector118 utilizes the range information output 124 to output the settingrange data C801 calculated in selector output 119, to the computing unit120.

At the timing T803, based on the setting range data C801, the computingunit 120 calculates the minimum voltage value 123 serving as the Vminand the maximum voltage value 122 serving as the Vmax for setting in theA/D converter 107. The upper limit voltage setting table 201 hereoutputs the ninth voltage value V9 to the upper limit voltage value 202and the eighth voltage V8 to the minimum voltage value 123.

At the next sampling timing T804, the A/D converter 107 sets the eighthvoltage value V8 in Vmin by way of the computing unit 120, and samplesthe output voltage 104 in the seventh range R7 where the ninth voltagevalue V9 is set in Vmax by way of the upper limit voltage setting table201. The power controller 112 outputs the data D802 serving as the datasignal 113 for the output voltage 104 sampled at the sampling timingT804, to the computing unit 117.

At the timing T805, the data signal 113 is input into the computing unit117. The computing unit 117 calculates the range of the output voltage104 controlled by the PWM signal 115 based on the data signal 113, andoutputs a computing unit (clock) output 128. The range of the outputvoltage 104 is changed based on duty of the PWM signal 115. The selector118 utilizes the range information output 124 to output the settingrange data C802 calculated in selector output 119, to the computing unit120.

At the timing T806, based on the setting range data C802, the computingunit 120 calculates the minimum voltage value 123 serving as the Vminand the maximum voltage value 122 serving as the Vmax for setting in theA/D converter 107. The upper limit voltage setting table 201 hereoutputs the tenth voltage value V10 into the upper limit voltage value202, and outputs the ninth voltage value V9 into the minimum voltagevalue 123.

At the next sampling timing T807, the A/D converter 107 sets the ninthvoltage value V9 in Vmin by way of the computing unit 120, and samplesthe output voltage 104 in the eighth range R8 where the tenth voltagevalue V10 is set in Vmax by the upper limit voltage setting table 201.The power controller 112 outputs the data D803 serving as the datasignal 113 for the output voltage 104 sampled at the sampling timingT807 to the computing unit 117.

At the timing T808, the data signal 113 is input into the computing unit117. The computing unit 117 calculates the range of the output voltage104 controlled by the PWM signal 115 based on the data signal 113, andoutputs a computing unit (clock) output 128. The selector 119 utilizesthe range information output 124 to output the setting range data C803calculated in the selector output 119, to the computing unit 120.

At the timing T809, based on the setting range data C803, the computingunit 120 calculates the minimum voltage value 123 serving as the Vmin,and the maximum voltage value 122 serving as the Vmax for setting in theA/D converter 107.

The operation from the sampling timing T801 to the timing T809 isrepeated from here onwards.

The power supply controller of the second exemplary embodiment asdescribed above is capable of controlling the minimum voltage value andthe maximum voltage value in the steady state period and thereforeperforms no unnecessary conversion in the reference voltage range sothat the A/D conversion speed can be accelerated.

In the above described first and second exemplary embodiments of theinvention, the computing unit 120 inputs a data signal that was theoutput signal of power controller circuit 112. The present inventionhowever is not limited to this example, and a difference voltage 111 maybe inputted as the deviation signal.

Further, it is noted that Applicant's intent is to encompass equivalentsof all claim elements, even if amended later during prosecution.

1. A power supply control method of performing a feedback control of anoutput voltage based on a deviation signal for a standard voltage valueserving as a target value for the output voltage and a digital signalgenerated by analog/digital (A/D) conversion of the output voltage, themethod comprising: selecting a range of the reference voltage for theA/D conversion based on the digital signal in a power supply startupperiod; and selecting a range of the reference voltage for the A/Dconversion based on the deviation signal or a signal corresponding tothe deviation signal in a steady state period.
 2. The power supplycontrol method according to claim 1, further comprising: setting therange of the reference voltage by changing a minimum voltage value ofthe reference voltage.
 3. The power supply control method according toclaim 1, further comprising: setting the range of the reference voltageby changing a maximum voltage value and a minimum voltage value of thereference voltage.
 4. The power supply control method according to claim1, wherein the range of the reference voltage includes a plurality ofrange levels, one of the range levels being selected based on a mostsignificant bit of the digital signal during the power supply startupperiod.
 5. The power supply control method according to claim 1, furthercomprising: generating a pulse width modulation (PWM) signal based on atleast one of the digital signal, the deviation signal or the signalcorresponding to the deviation signal, wherein the output voltage iscontrolled based on the PWM signal.
 6. The power supply control methodaccording to claim 5, wherein the range of the reference voltageincludes a plurality of range levels, one of the range levels beingselected based on a duty of the PWM signal during the steady stateperiod.
 7. The power supply control method according to claim 1, whereinthe range of the reference voltage includes a plurality of range levels,a maximum voltage value of each of the range levels is equal to eachother, and a minimum voltage value of each of the range levels isdifferent to each other.
 8. The power supply control method according toclaim 7, wherein the plurality of range levels are set as a binary-codedrange information.